Electromechanical atomizer apparatus



Oct. 10, 1967 B. J. EISENKRAFT I 5,

ELECTROMECHANICAL ATOMIZER APPARATUS Filed Oct. 5, 1964 2 Sheets-Sheet 1INVENTOR Bernard J. E/sen/rraff BY 6* $1M ATTORNEY Oct. 10, 1967 B. J.EISENKRAFT 3,346,189

ELECTRQMECHANICAL ATOMIZER APPAR TUS Filed 00 5, 1964 2 Sheets-Sheet 2 pI J 59 INVENTOR ATTORNEY w \\\\\\\k/UO WWW W7 I am/ 1,

M 1 pr: 4 \x lllllllllll L /0 g I. Bernard J B'sen/rraf/ United StatesPatent 3,346,189 ELECTROMECHANICAL ATOMIZER APPARATUS Bernard J.Eisenkraft, 1043 E. 81st St., Brooklyn, N.Y. 11236 Filed ()et. 5, 1964,Ser. No. 401,503 11 Claims. (Cl. 239-102) ABSTRACT OF THE DISCLOSURE Anatomizing bar, mounted to a drive rod extending through a bore in thecentral pole of a pot magnet, is vibrated by means of AC. currentpassing through a winding around one end of the drive rod and reactingwith the field of the magnet. A heating element extends through thedrive rod and around a recess in the periphery of the bar. The bar mayhave more than two arms radiating from a central point and may also bespecially coated with material wettable by the liquid being atomized. Inanother species, an atomizing cylinder adjacent the central pole of apot magnet is vibrated by AC. current passing through a driving coiladjacent the central pole of tre magnet.

This invention relates generally to apparatus for dispersing a liquidinto finely divided droplets and, specifically, to electromechanicalatomizer apparatus for this purpose.

There are numerous areas in many industries, notably the chemical,pharmaceutical and metallurgical fields, that require the production offinely divided particles from a substance in liquid form. The substancemay be liquid at ambient temperatures, or may exist as a liquid only atelevated temperatures. Thus, in a spray chilling process, solidsubstances are heated to the liquid state and, in this state, areatomized in air which may be at ambient temperature, the finely dividedparticles freezing to a beaded powder which comprises sphericaldroplets. My earlier patents, US. 2,779,623 and 3,038,532, discloseelectromechanical atomizer apparatus eminently suited to the foregoingapplications, particularly in the field of spray chilling, and I haveproduced with such apparatus beaded powders having a size distributionof approximately 100- 1000 microns with unusually narrow sizedistribution, practically eliminating dusting problems and furthersieving.

The present invention is directed to improvements in theelectromechanical atomizers disclosed in my earlier patents. In oneaspect of my invention, an improved electromechanical transducer isprovided to drive vibrating bar means or vibrating cylinder means. Inanother aspect of my invention, means are provided for heating thevibrating bar means while in operation. In yet another aspect of myinvention, a cruciform arrangement of vibrating bar means is providedfor operation by a single electromechanical transducer to increase thecapacity of the system.

One of the objects of my invention is to provide improvedelectromechanical atomizer apparatus.

Another object of my invention is to provide electromechanical atomizerapparatus employing improved electromechanical transducer means.

A further object of my invention is to provide electromechanicalatomizer apparatus which includes mean-s to heat the vibrating bar whilethe same is in operation.

Still another object of this invention is to provide electromechanicalatomizer apparatus employing a cruciform arrangement of vibrating barsoperated by a single electromechanical transducer to increase thecapacity of the system and the concentration of atomized droplets in afixed area.

Yet a further object of this invention is to provide electromechanicalatomizer apparatus in which the pickup for the feedback circuit islocated at a distance from the vibrating bar and well away from theliquid spray area.

Still a further object of this invention is to provide electromechanicalatomizer apparatus employing an improved electromechanical transducerwith a cylindrical atomizin g element.

Another object of this invention s to provide an atomizing member with asurface that is wettable by the liquid being atomized for optimumatomization and narrow droplet size distribution.

Other and further objects of my invention will become apparent duringthe course of the following description.

Referring now to the drawings in which like numerals represent likeparts in the several views:

FIGURE 1 represents a view in elevation, partially diagrammatic, showingone form of the present invention.

FIGURE 2 represents an enlarged medial section of the electromechanicaltransducer and vibrating bar shown in FIGURE 1.

FIGURE 3 represents an enlarged perspective view of the vibrating barand drive rod and showing the means for heating the vibrating bar Whilethe same is in operation.

FIGURE 4 represents a transverse section of the bar of FIGURE 3, takenalong the line 4-4 of FIGURE 3.

FIGURE 5 represents a perspective view of the cruciform vibrating bararrangement.

FIGURE 6 represents a medial vertical section of another form ofelectromechanical transducer with a cylindrical atomizing element,showing also in diagrammatic form the related circuitry and feed means.

Referring now to the form of invention shown in FIG- I URE l,electromechanical transducer 1 is provided with drive rod 2 rigidlyconnected to atomizing bar 3 at the center thereof. Electromechanicaltransducer 1 is powered by the circuitry encompassed by block 4, whichcircuitry is shown diagrammatically as comprising a preamplifier 5,phase shifter 6 and power amplifier 7. As taught in my U.S. Patent2,779, 623, power amplifier 7 drives electromechanical transducer 1through line 8, said electromechanical transducer 1 in turnreciprocating drive rod 2 thereby causing atomizing bar 3 to vibrate, itbeing apparent that the point of connection of drive rod 2 withatomizing bar 3 will be an antinode. Feedback line 9, connected to meansin the electromechanical transducer 1 electrically responsive to thevibrations of drive rod 2 and atomizing bar 3 which means willhereinafter be described, communicates to preamplifier 5 an electricalsignal indicative of the state of vibration of atomizing bar 3 andsensing any tendency of atomizing bar 3 to depart from vibrating at theresonant flexural mode to which it has initially been tuned to vibrate.This preamplified signal is fed through line 10 to phase shifter 6 andthence through line 11 to power amplifier 7, whereby the output of poweramplifier 7 is corrected and adjusted to maintain atomizing bar 3vibrating at the desired resonant fiexural mode, all as taught by my USPatent 2,779,623. Reservoir 12, provided with valved feed line 13,introduces liquid feed 14 to be atomized to a face of said atomizing bar3 which disperses said liquid feed 14 into a spray 15 of finelydispersed droplet-s. Instead of the one valved feed line 13 shown inFIGURE 1, additional valved feed lines 13 leading to other portions ofatomizing bar 3 may be employed.

The electromechanical transducer 1 of FIGURE 1 is shown in enlargedmedial section in FIGURE 2, it being understood that suchelectromechanical transducer is generally circular in plan and hencesymmetrical about the longitudinal axis thereof. Electromechanicaltransducer 1 comprises magnet 16 provided with a central pole 17 havinga bore 17a through which drive rod 2 freely extends. Magnet 16 is Whatis commonly termed a pot magnet, and the field coil winding is indicateddiagrammatically by diagonal lines. Diaphragm 18 mounted on drive rod 2and supporting coil form 19 concentrically with respect to drive rod 2is connected through resilient ring 20 with flange 21. Power coil 22,wound around coil form 19 and extending into annular gap 23 between thecentral pole 17 and the outer pole 17b of pot magnet 16, is connected topower amplifier 7 through line 8. Metallic guide disc 24 is secured, asby welding or soldering, to drive rod 2 and is also secured at itsperiphery to dia phragm 18, for example by a bead 25 of an epoxy typecement. Guide disc 26, which may for example be of rubber, is mounted todrive rod 2 and is secured to bell housing 27, assuring rectilinearmotion of drive rod 2. Screws 28 mount bell housing 27 and flange 21securely to magnet 16. That end of drive rod 2 remote from atomizing bar3 is provided with rod magnet 29 extending upwardly therefrom throughbore 30 of pickup coil form 31 mounted to bracket 32, the latter in turnbeing mounted to magnet 16 by means of screws 33. Pickup coil 34, woundaround pickup coil form 31, communicates with preamplifier through line9.

In the operation of the apparatus shown in FIGURES 1 and 2, the ACoutput of power amplifier 7 is fed through power coil 22 generating analternating magnetic field which reacts with the magnetic field of potmagnet 16 causing diaphragm 18 to vibrate and also drive rod 2 toexecute longitudinal vibrating motion. In this manner, atomizing bar 3is caused to vibrate at the selected resonant flexural mode. Rod magnet29 at the remote end of drive rod 2 also vibrates in unison with driverod 2 and, pickup coil 34 being in close proximity thereto, analternating current is generated in said pickup coil 34, whichalternating current corresponds with the vibrative state of atomizingbar 3 and senses any tendency of said atomizing bar 3 to depart from theresonant flexural mode to which it has been driven, said alternatingcurrent being fed through line 9 to preamplifier 5 and thence to phaseshifter 6 as taught by my U.S. Patent 2,779,623, whereby the output ofpower amplifier 7 is corrected and adjusted to maintain atomizing bar 3vibrating at the selected resonant flexural mode as shown by the dashedlines in FIGURE 2. Meanwhile, liquid feed 14 is introduced fromreservoir 12 through valved feed line 13 to said atomiz'ing bar 3 foratomization thereon.

If feed 14 is normally solid at ambient temperatures, and this may forinstance apply to various metals, urea, stearic acid, waxes,naphthalenes, etc., reservoir 12, valved feed line 13 and atomizing bar3 will require heating to maintain their respective temperatures abovethe melting point of the substance to be atomized in part to liquefy thesaid substance and also to prevent premature freezing of the substanceonce it has been liquified and before it has been atomized. Reservoir 12and valved feed line 13 may be heated by any means known to the art.FIGURES 3 and 4 show means for heating atomizing bar 3 while it is inthe vibrative state. Atomizing bar 3 is provided around its peripheryand on its neutral axis with an inwardly etxending slot 35. Drive rod 2is hollow for at least part of its length and its interior communicateswith bore 36 which in turn communicates with slot 35. Resistance heatingwire 37, covered by insulation 38 such as fiberglass braid, is placed inslot 35 around atomizing bar 3, and is held in place by cement packing39. Wire 37 leads through bore 36 into the interior of drive rod 2 andthence to line 40 exiting from drive rod 2 at a convenient point andconnecting to a. suitable source of electrical power.

An alternate form of atomizing bar for use with electromechanicaltransducer 1, with or without means for heating the same, is shown inFIGURE 5. As shown, bar 3a comprises a cruciform arrangement of arms 41of equal length, drive rod 2 being rigidly connected to the intersectionthereof, said intersection'being an antinode and arms 41 vibrating asshown by the dashed lines. Atomizing bar 3a may be fabricated from asingle sheet of metal. Liquid feed may be fed through valved feed lines(not shown in FIGURE 5) to the ends of each of the arms 41 for increasedatomization capacity of the system. Symmetrical arrangements of threearms 41, or five or more arms 41, may also be employed, so long as thearms 41 are symmetrical about their intersection to which drive rod 2 isconnected.

Referring now to the form of invention shown in FIGURE 6, anelectromechanical transducer similar to that shown in an articleappearing in Review of Scientific Instruments, May 1941, at ages 250256, entitled An Electromagnetic Sound Generator for Producing IntenseHigh Frequency Sound, is employed with liquid feed means to provide aunique electromechanical atomizer for dispersing a liquid into finedroplets. Thus, electromechanical transducer 42 comprises pot magnet 43with a central pole 44 and an outer pole 45, field windings beingindicated diagrammatically by diagonal lines. A magnetically permeableannular disc 46 is mounted to outer pole 45 concentrically to centralpole 44 leaving annular gap 47 thereabout. Metallic tubular sections 48,flanged as at 49 for ease in assembling the same to each other and topot magnet 43 are provided with circular notches for a purpose whichwill hereinafter appear, and screws 51 secure the said tubular sections48 to each other and, through disc 46, to pot magnet 43. A solidmetallic cylinder 52, provided with integral medial transverselyextending flange 53 and integral coaxial longitudinally extending ring54 is mounted within tubular sections 48, flange 53 extending intonotches 50 and resiliently held therein by rubber shims 55 covered withaluminum or other metallic foil 56 so as to electrically ground flange53, and hence cylinder 52, to tubular sections 48 and pot magnet 43.Ring 54 extends into gap 47. Insulating disc 57 is mounted to the top ofcentral pole 44, and a thin metallic disc 58 is mounted to the top ofdisc 57, insulated thereby from central pole 44. It will be noted thatdisc 58 is vertically spaced from the bottom of cylinder 52 so as toconstitute one side of a capacitor the value of which varies with thedimension of the air gap between cylinder 52 and disc 58. Shielded wire59 communicates between disc 58, through perforation 60 in disc 57 andbore 61 in central pole 44, and preamplifier 5 through line 9. Thepotential of the other side of the said capacitor is, as previouslymentioned, the same as that of the pot magnet 43 and a line therefrom tothe preamplifier may be provided, as line 62 shown as communicating withone of the elements of line 9, it being understood that line 9 isactually a pair of wires.

Driving coil 63 is wound around central pole 44 adjacent ring 54, and ispowered from power amplifier 7 through line 8 extending through bore 64in outer pole 45 and insulated therefrom, it being understood that line8 is actually a pair of wires 65 communicating with the two ends ofdriving coil 63.

In operation, disc 58 may be charged relative to the bottom of cylinder52 through wire 59 by suitable means to approximately 300 volts, forexample. Alternating electric current from power amplifier 7 is fedthrough line 8 to driving coil 63. Ring 54 adjacent driving coil 63 hasinduced in it alternating currents. Attraction and repulsion of magneticfields in gap 47 produces vibratory motion of cylinder 52 which isinitiated at a selected resonant flexural mode. The capacitorcomprising, as plates thereof, the bottom of cylinder 52 and disc 58,will fluctuate in value and sense any tendency of cylinder 52 to departfrom vibrating at the selected resonant flexural mode. Meanwhile, liquidfeed 14 is introduced from reservoir 12 through valved feed line 13 tothe top of cylinder 52. for atomization thereon.

For optimum atomization and narrow droplet size distribution, the liquid(including heated substances such as metals which are normally solid atambient temperatures) should wet the surface of the atomizing member(bar 3 or St: or the top surface of cylinder 52). The atomizing memberis usually metallic and, if it is clean and free from contaminants,organic and inorganic solutions and melts readily wet the atomizingmember. However, when atomizing molten metals, the materials from whichthe atomizing member is made should be carefully selected to promotewetting by the metal being atomized. Thus, when atomizing molten solderfrom a stainless steel atomizing member, the solder does not wet theatomizing member and poor atomization may result. If, however, thesurface of the stainless steel atomizing member is previously coatedwith a solder of higher melting point or clad with a metal that is wetby the molten solder, optimum atomization of the molder solder will beattained. With some metal melts to be atomized, it can be broadly statedthen that, Where the base metal itself constituting the atomizing memberis not readily wet by the metal being atomized, the atomizing member canbe coated with a layer of another metal, a ceramic or a ceramet, thecoating being chosen so as to be wet by the metal being atomized. Whilethe meaning of the term wet as herein employed should be clear to thosefamiliar with the art, it will be stated for purposes of clarity and infull compliance with the statute that, when a substance such as moltenmetal wets the atomizing member, this means that the substance forms afilm on the atomizing member (strictly speaking, on the atomizing faceof the atomizing member) and, conversely, when a substance such as amolten metal does not wet the atomizing member, this means that thesubstance does not form a film on the atomizing member but ratherappears as drops or balls on the said atomizing member.

While I have shown the best embodiments of my invention now known to me,I do not wish to be limited to the exact structures shown and describedherein, but may use such substitutions, modifications or equivalents asare embraced within the scope of the specification and drawings andclaims.

I claim:

-1. Atomizing apparatus to disperse a liquid into fine droplets,comprising:

(a) a pot magnet having:

a central pole,

an annular outer pole surrounding said central pole in concentricrelation therewith,

an annular gap between said central pole and said annular outer pole,

(b) electrically conductive means interposed in said annular gap andadapted to react with the magnetic field of said pot magnet,

(c) a source of alternating electric current in electrically operativerelation with said electrically conductive means,

((1) atomizing means connected to said electrically conductive means andadapted to be vibrated thereby,

(e) means to deliver liquid to be atomized to a face of said atomizingmeans,

(f) pickup means adjacent said atomizing means and adapted to haveimpressed thereon an electrical value responsive to the vibrative stateof said atomizing means,

g) phase shifting means placing the electrical value impressed on saidpickup means in modulating relationship with said source of alternatingelectric current to maintain said atomizing means vibrating at aresonant fiexural mode.

2. Apparatus as in claim 1, further comprising:

(h) said atomizing means comprising a cylinder,

(i) said electrically conductive means comprising a metallic ringsecured to said cylinder.

3. Apparatus as in claim 2, further comprising:

(j) said pickup means comprising a capacitor having:

a conductive disc interposed between one face of said cylinder and saidcentral pole, said conductive disc being spaced from said one face ofsaid cylinder,

means insulating said conductive disc from said central pole,

means charging said conductive disc relative to said cylinder,

means communicating the capacitance of said capacitor to said phaseshifting means.

4. Apparatus as in claim 3, further comprising:

(k) said source of alternating electric current comprisa poweramplifier,

a driving coil wound around said central pole adjacent said metallicring,

electric conduit means communicating between said power amplifier andsaid driving coil.

5. Apparatus as in claim 1, further comprising:

(h) said central pole having a bore extending completely therethroughalong the longitudinal axis of said central pole,

(i) said atomizing means comprising:

.a bar,

a drive rod secured to the central portion of said bar and extendingthrough said bore.

6. Apparatus as in claim 5, further comprising:

(j) a coil form secured to said drive rod and extending into saidannular gap,

(k) said electrically conductive means comprising a coil wound aroundsaid coil ttorm.

7. Apparatus as in claim 6, further comprising:

(1) a magnetic member secured to that end of said drive rod remote fromsaid bar,

(in) a coil form secured to said pot magnet and having a bore throughwhich said magnetic member extends,

(u) said pickup means comprising ,a coil wound around said lastmentioned coil form.

8. Atomizer apparatus to disperse a liquid into droplets comprising:

(a) a pot magnet having:

a central pole,

an annular outer pole surrounding said central pole in concentricrelation therewith,

a bore extending through said central pole along the longitudinal axisof said pot magnet,

an annular gap between said central pole and said annular outer pole,

( b) drive rod means extending through said bore and having a first endand a second end,

(c) power coil means secured to said drive rod means and extending intosaid annular gap,

(d) atomizing bar means secured to said first end of said drive rodmeans and adapted to be vibrated thereby,

(e) magnet means secured to the second end of said drive r-od means,

(f) pickup coil means adjacent said magnet means and adapted to haveinduced therein electrical currents when said magnet means isreciprocated by said drive rod means relative to said pickup coil means,

(g) a source of alternating electric current in communication with saidpower coil means,

(h) means placing the electrical currents induced in said pickup coilmeans in modulating communication with said source of alternatingelectric current to maintain said atomizing bar means vibrating at aresonant flexural mode,

(i) means to introduce liquid to be dispersed to a face of saidatomizing bar means.

9. Apparatus as in claim 8, further comprising:

(j) a slot formed around the periphery of said atomizing bar meansadjacent the neutral axis thereof, said slot extending inward-1y fromthe periphery thereof,

(k) a bore in said drive rod means,

(1) a bore in said atomizing bar means communicating between said firstmentioned bore and said slot,

(m) an electrical heating element extending through said bores from saiddrive rod to said slot and along said slot,

I (11) means to retain said electrical heating element in said slot. I

10. Apparatus as in claim 8, further comprising:

(j) said atomizing bar means comprising more than two armssymmetrical-1y radiating from a central point,

p (k) said drive rod means being rigidly secured to said central point.11. Atomizing apparatus adapted to be vibrated by an electromechanicaltransducer, comprising:

(a) drive rod means adapated to be reciprocated by saidelectromechanical transducer, (b) atomizing bar means rigidly secured atits center to said drive rod means,

(c) a slot formed around the periphery of said atomizing bar meansadjacent the neutral axis thereof, said slot extending inwardly from theperiphery thereof,

(d) a bore in said drive rod means,

(e) an electrical heating element extending through said bore and alongsaid slot, (f) means to retain said electrical heating element in saidslot.

References Cited UNITED STATES PATENTS 2,481,620 9/ 1949 Rosenthal239102 2,577,853 12/1951 Kurata 23999 3,021,077 2/1962 Gauthier 239-153,123,305 3/1964 Eisenkraft 239-102 3,189,280 6/1965 Drayer 239102FOREIGN PATENTS 1,041,879 10/1958 Germany.

EVERETT W. KIRBY, Primary Examiner.

M. HENSON WOOD, 1a., R. S. STROBEL, Examiners.

1. ATOMIZING APPARATUS TO DISPERSE A LIQUID INTO FINE DROPLETS,COMPRISING: (A) A POT MAGNET HAVING: A CENTRAL POLE, AN ANNULAR OUTERPOLE SURROUNDING SAID CENTRAL POLE IN CONCENTRIC RELATION THEREWITH, ANANNULAR GAP BETWEEN SAID CENTRAL POLE AND SAID ANNULAR OUTER POLE, (B)ELECTRICALLY CONDUCTIVE MEANS INTERPOSED IN SAID ANNULAR GAP AND ADAPTEDTO REACT WITH THE MAGNETIC FIELD OF SAID POT MAGNET, (C) A SOURCE OFALTERNATING ELECTRIC CURRENT IN ELECTRICALLY OPERATIVE RELATION WITHSAID ELECTRICALLY CONDUCTIVE MEANS, (D) ATOMIZING MEANS CONNECTED TOSAID ELECTRICALLY CONDUCTIVE MEANS AND ADAPTED TO VIBRATED THEREBY, (E)MEANS TO DELVIER LIQUID TO BE ATOMIZED TO A FACE OF SAID ATOMIZINGMEANS, (F) PICKUP MEANS ADJACENT SAID ATOMIZING MEANS AND ADAPTED TOHAVE IMPRESSED THEREON AN ELECTRICAL VALUE RESPONSIVE TO THE VIBRATIVESTATE OF SAID ATOMIZING MEANS, (G) PHASE SHIFTING MEANS PLACING THEELECTRICAL VALUE IMPRESSED ON SAID PICKUP MEANS IN MODULATINGRELATIONSHIP WITH SAID SOURCE OF ALTERNATING ELECTRIC CURRENT TOMAINTAIN SAID ATOMIZING MEANS VIBRATING AT A RESONANT FLEXURAL MODE.